The Radiation Oncology Branch (ROB) of NCI is currently developing an electron spin resonance (ESR) imaging system. ESR spectroscopy systems usually operate at frequencies of about 10 GHz; however, in order to get sufficient tissue penetration to perform imaging, the ROB's system will work at a considerably lower frequency (e.g., 250 MHz). The line widths of typical ESR spectra are such that larger magnetic field gradients are needed for ESR imaging than for nuclear magnetic resonance imaging. The goal of this project is twofold: (1) to design a gradient coil system capable of producing magnetic field gradients on the order of 100 G/cm, to be used in the ROB's ESR imaging system; and (2) to assist the ROB in exploring the trade-offs between spatial resolution, tissue penetration, signal-to-noise ratio, and difficulty of construction that occur when modifying existing hardware and concepts from NMR imaging and ESR spectroscopy so that they apply to ESR imaging.